Allow to connect without a dbname param

The PDO connection allow the instantiation of the connection even if the dbname
parameter isn't present. This change is there to make sure both behave the same way.

Fix pg boolean conversion

PG specific attribute PDO::PGSQL_ATTR_DISABLE_NATIVE_PREPARED_STATEMENT is now only set when it is still supported

reverted @deeky666 suggestion. Since it failed on testBooleanNullConvertsToPHPValue test. 
with message Failed asserting that true is null.
Since I moved this code from BoolenType::convertToPHPValue in the first place, I presume the code there correct.

Updated test for uppercased values

updated convert function  to include uppercased values

Description fix

fixed parameter order in conditions

Changes after Ocramius comments